1. Field of the Invention
The present invention relates to an optical disk drive, and an object lens actuator and an optical pickup constituting the optical disk drive.
2. Description of Related Art
In recent years, a densification of an optical disk advances and, to cope with the trend, a wavelength of a laser is shortened or an aperture of an object lens is expanded. In such a situation, a tilt of an object lens from an optical disk tends to increasingly influence a quality of an optical spot. A signal deterioration of the optical spot caused by the tilt of the object lens leads to the signal deterioration at record/read and hence it comes to be necessary to reduce the angle (tilt) between the optical disk and the object lens.
Such optical disk drive has an object lens actuator to drive the object lens to condense a light on a recording surface of the optical disk in a focusing direction (in a direction close to/away from an optical disk surface), in a tracking direction (in a radial direction of the optical disk), in a radial tilt direction (tilting toward a direction of an optical disk radius), and in a tangential tilt direction (tilting toward a direction of a tangential line of the optical disk).
A moving part support equipment including a holder equipped with the object lens and coils of the object lens actuator is arranged so that elastic support parts one end and the other end of each of which are fixed to a moving part and a fixed part respectively, namely plural straight springs, may form a parallel link.
Document 1 (Japanese Patent Laid-open No. 2003-228852) discloses an optical pickup provided with an actuator having a taper and a screw, which does not require securing a space for skew adjustment of an object lens to an optical disk on a side of an optical system location.
Further, Document 2 (Japanese Patent Laid-open No. 2006-236437) and Document 3 (Ricoh Technical Report No. 31, pp. 47 to 51 (2005)) disclose an optical disk system having plural coils in a lens holder and an actuator of four axes including an axis in the tangential tilt direction.
The optical disk system described in Document 2 and Document 3 is configured so as to control a lens holder in four directions including the tangential tilt direction.
However, since the lens holder has plural coils including a tangential tilt drive coil, the mass of the lens holder increases and the control of tilt in two directions is complicated.
An object of the present invention is to provide an object lens actuator, an optical pickup, and an optical disk drive, which can reduce a mass of a coil installed on a lens holder and thus reduce a moment of inertia of the lens holder, can increase a size of the object lens actuator to drive the object lens in the tangential tilt direction, and can drive and control the lens holder with a small amount of drive current.